This invention relates generally to telephony, and more particular concerns the detection of current flowing in a pair of telephone wires.
It becomes necessary, in telephone subscriber circuits, to determine when current is flowing in a pair of wires. The current detection circuit must not affect voice frequencies on the pair, and must pass high AC voltages used to ring a telephone. To our knowledge, no prior detection method provided the unusual advantages in operation and results as now afforded by the present invention, as will appear.